Decline of Small and Native Species (SNS) in Mt. Isarog National Park: Impacts of Illegal Fishing and Introduced Exotic species

Raul G Bradecina Vol 10 No 1 (2007), pp. 24-33

Abstract:

The assessment of the impact of introduced exotic fish species into the small and native fish species covered 18 major rivers and 31 creeks spread all over 6 municipalities and a city bordering Mt. Isarog Natural Park (MINP). Considered as a distinct sub-region of the Southern Luzon biogeography zone because of its high genetic, species, and ecosystem diversity, other form of threats exist in MINP aside from the threats still perpetrated by forest-edged communities and external interest that caused the destruction of its natural habitats and degradation of interacting ecosystems.

The population of introduced fish species relatively increased by more than a quarter in tenyears time. From the combined estimated annual catch from both fishing methods used, the proportion of introduced fish species increased by 10% in 1988 to more or less one half of their proportions in catch relative to the native fish species in 2002. While the proportion of the endemic fish species relative to the introduced fish species caught from the same methods dropped from more than 80 percent to a little more than 50 percent over the ten-year period.

It demonstrated that the introduction of exotic species has negatively affected the availability and the diversity of SNS in MINP areas with only the introduced fish species commonly sighted, while the sightings of the most endemic ones have become uncommon to extremely rare in the areas considered. Particularly, the invasion of introduced species to MINP waters in all probability caused the reduction of abundance of the native catfish to alarming level and could eventually lead to extinction. Biodiversity conservation measures should be implemented, assessment of the population of SNS, habitat enhancement, and repopulations strategies.